1. Field of the Invention
This invention relates to a method and to an apparatus for balancing a tool and more particularly to a method and an apparatus for distributing weighted objects in spatial relation to the tool in order to balance the tool.
2. Discussion
Machine tools are used in a wide variety of manufacturing applications requiring highly precise cutting, milling, boring, shaping, drilling, or other sorts of activities. Normally a variety of unique tools and associated tool holders are placed into a automated tool magazine and then are automatically placed, as needed, into an operative position by means of a tool changer operating under stored program control. The operative tool, so chosen, is run or activated at a relatively high speed for a pre-determined amount of time necessary for the chosen tool to perform its desired operation. In fact, such tool operational speeds may exceed 10,000 rotations per minute (rpm) and may include tool accelerations and decelerations of approximately 2,000-5,000 rpms per second.
While these tools have been very successful in performing their needed and highly precise functions, they have also experienced difficulties in meeting or maintaining these highly precise standards, over a period of time, due to imbalances. These imbalances arise from such things as normal wear of the tool, wear associated with the tool holding apparatus into which the tool resides and or is coupled, design of the tool holding apparatus, and manufacturing technologies employed to make the tool holding apparatus. Typical levels of imbalance usually approach approximately 60 gram millimeters.
In order to consistently maintain the high quality of the goods manufactured by means of these high-speed tools, it is necessary to correct for these imbalances by performing a balancing operation upon the tool. Such a balancing operation must, however, occur very quickly and with a high degree of repeatability because of the high speed of the tools used and because of the repeated use of the same tools. If a manual balance were accomplished, much time would be wasted from the desired manufacturing activities resulting in a waste of resources and a lack of productivity.
While there currently exists a number of balancers, these balancers have been found to inadequately balance such high-speed machine tools. For instance, a "waterwheel" balancer is generally not capable of operating at such high speeds since air being carried by the balancer prevents the water stream from properly being directed into the appropriate chamber. In fact, even if, the water stream was properly directed into the chamber, the high rotational speed of the tool would tend to atomize the water stream as it hit the chamber wall, resulting in an incorrect balance. Additionally, the waterwheel has been found to be much too slow to achieve the desired tool balance and is not capable of repeating a previous balance condition for a specific tool, resulting in increased time necessary to once again achieve a previously known and now needed balance state.
In contrast, the "counterbalance" balancer is faster than the waterwheel as it requires simply a motor and a plurality of gears to appropriately position weights in variable positions, wherein a specific weight and the position of that specific weight are selected by "trial and error." While the counterbalance balancer is relatively fast, it becomes inoperative at the relatively high tool speeds since the gears and other associated structural components tend to fail at these speeds. Additionally, this "trial and error" approach provides a balancing operation which is still considered to be slow and fails to offer the desired ability to repeat known prior balance states, when these previously known and/or derived balance states are needed again. Such a failure to repeat these balance states results in additional time spent in unnecessary "trial and error" activities. The counterbalance balancer is therefore considered to be inappropriate for use with such high speed tools as are the other known types of balancers.